Study On The Comprehensive Recovery Techonolgy Of Secondary Zinc Oxide From Smelting Industery Waste Residue

Secondary zinc oxide is a kind of secondary zinc resource with complex chemical components.It is a production of re-oxidation of smelting waste containing zinc after high temperature reduction,volatilization and enrichment.Its chemical composition fluctuates greatly due to different sources of waste containing zinc.It usually contains zinc oxide,iron oxide,lead oxide,nickel,cadmium,indium and other oxides,with high impurity content and difficult recovery and utilization.Therefore,this paper studies the acid leaching purification process of secondary zinc oxide,and the leaching behavior of secondary zinc oxide and its zinc leaching residue in deep eutectic solvents,so as to maximize the recovery and utilization of zinc.The specific contents are as follows:(1)a two-stage sulfuric acid leaching process of secondary zinc oxide(containing zinc38.22%)was designed and studied.The specific process conditions are as follows:(1)chlorine removal:p H 8,liquid-solid ratio 5:1,temperature 50°C,time 60 min;(2)medium leaching:initial acidity 1.6 mol·L^-1,liquid-solid ratio 4:1,temperature 70°C,time 2 h;(3)acid leaching:initial acidity 2.10 mol·L^-1,liquid-solid ratio 4:1,temperature 80°C,time 2 h;(4)iron removal:H₂O₂dosage is equal to 2 times the theoretical dosage,p H 4,temperature70°C,time 1 h;(5)manganese removal:KMn O₄ dosage is equal to 2 times the theoretical dosage,p H 5,time 1 h;(6)heavy metals removal:Except heavy metals:zinc powder dosage is equal to 3 times the theoretical dosage,temperature 50°C,time 30 min;concentrated crystallization:baume degree 55°Be,(7)crystallization time 10 h,terminal temperature25°C.Under this condition,the total recovery rate of zinc was 82.2%,and the zinc-containing phase of the zinc leaching residue after treatment is zinc ferrite which is hard to dissolve.(2)the leaching behavior,leaching mechanism and leaching kinetics of secondary zincoxide by betaine hydrochloride-urea(15:85)DES(BH-U(15:85)DES)was studied.The results showed that when the liquid-solid ratio was 10:1,the temperature was 70°C,the time was 4 h and the stirring rate was 400 r·min^-1,the zinc leaching rate is the highest.The leaching mechanism is that the carboxyl and amine groups in Zn O and BH-U(15:85)DES are leached.The leaching process conforms to the interface chemical reaction model,and its apparent activation energy E=40.69 k J·mol^-1.The leaching rate of BH-U(15:85)is 91.2%,the leaching solution can be used for electrodeposition of zinc in non-aqueous system,and the unleached zinc remains as zinc ferrite in the residue phase.(3)The zinc leaching residue of the acid leaching process was used as a typical sample of low zinc content waste to carry out zinc ferrite decomposition and leaching research.A series of choline chloride-based DESs were synthesized,and choline chloride-oxalic acid DES(Ch Cl-OA DES)was selected for in-depth study based on zinc ferrite dissolution and zinc leaching rate.Ch Cl-OA DES was used as leaching agent to zinc leaching residue.The changes of zinc leaching rate under different factors and cyclic use were investigated.The results showed that when the molar ratio of Ch Cl and OA was 1:1,the liquid-solid ratio was10:1,the temperature was 60°C,the time was 3 h and the stirring rate was 500 r·min^-1,the zinc leaching rate was 95.0%at most.After four cycles,the zinc leaching rate can still reach88.7%.The coordination reaction and salt formation reaction of-COOH in Ch Cl-OA DES can decompose Zn Fe₂O₄,and the different oxalates generated are separated due to the difference in solubility,in which Zn C₂O₄·2H₂O enters the releaching solution and is recovered.The leaching process conforms to the interface chemical reaction model,and its apparent activation energy E=58.01 k J·mol^-1.